What is your timing curve?

[Kern Dog]

Here we go.

It may not be drawn like what you’re used to seeing but this made sense to me. It starts at an initial of 20 degrees at the 1000 rpm idle. This cam needs a bit more idle speed so that is why I’m not at 750 rpms like many others.
It doesn’t advance at all until 1750 rpms but between 1750 and 2250, it jumps around 9 degrees then slows down to top out at 33. 13 degrees total advance.
This was my curve to account for my higher compression I had awhile back.
It sure looks like I can improve on it.
13 degrees over 1250-1500 rpms and all of it coming in so late.

 

[Budnicks]

We've tried, members have tried....seems like everyone needs to start their own thread to get answers.

I know @dadsbee is one who lets people know there is a search function here....but do the people listen???

Preaching to the choir Bob.

I recommend it often even in the Welcome wagon, to newbies...

pat myself on the back

 

[Budnicks]

Interest read here...

 

[Kern Dog]

This chart is with the new Hi-Rev distributor from Rick Ehrenberg. It has not been modified in any way, this is how it came to me. I did check the reluctor to pickup gap. It was within spec.

Notice how it instantly starts advancing right from idle. This gains 11 degrees in the same range that the MP distributor gained 1 degree. My timing light has a dial on it like so:

So I could be a degree off on how I read it when it is not right pointed at a number.
Still, this Hi Rev advances immediately off idle. The engine ran smoother as a result. Look at how it skyrocketed around 2750! I was surprised to see 50 degrees at 3000 rpms!
The FBO plate has limits in 2 degree increments.

Knowing that I don’t knock at the 33 degrees I was at before, it is safe to say that I can do that again.
I had it set to 20 degrees initial to improve idle quality but didn’t know until today that no advance came in until 1750 rpms.
I’m going to put this FBO plate in to limit to 14 degrees. In theory and by going by the graph, this should put me at 34 degrees about 2100 rpms.

MP curve on top, Hi Rev on the bottom.

 

[kiwigtx]

I tried using the search feature.
It is far from perfect. It often fails to bring up threads of mine even when I phrased the question in the same manner as the thread title.

That's possibly because you start so many damn threads that the SEARCH function is overwhelmed by the vastness of your spread on topics.

Maybe we should MERGE all of your threads into one, then it would easier for you to find it.

 

[kiwigtx]

This chart is with the new Hi-Rev distributor from Rick Ehrenberg. It has not been modified in any way, this is how it came to me. I did check the reluctor to pickup gap. It was within spec.

View attachment 1645653

Notice how it instantly starts advancing right from idle. This gains 11 degrees in the same range that the MP distributor gained 1 degree. My timing light has a dial on it like so:

View attachment 1645654
View attachment 1645655

So I could be a degree off on how I read it when it is not right pointed at a number.
Still, this Hi Rev advances immediately off idle. The engine ran smoother as a result. Look at how it skyrocketed around 2750! I was surprised to see 50 degrees at 3000 rpms!
The FBO plate has limits in 2 degree increments.

View attachment 1645657

Knowing that I don’t knock at the 33 degrees I was at before, it is safe to say that I can do that again.
I had it set to 20 degrees initial to improve idle quality but didn’t know until today that no advance came in until 1750 rpms.
I’m going to put this FBO plate in to limit to 14 degrees. In theory and by going by the graph, this should put me at 34 degrees about 2100 rpms.

MP curve on top, Hi Rev on the bottom.

View attachment 1645658

Are you sure that is not the graph showing school class-size numbers and the pay rate of teachers required for that quantity of children???

 

[moparedtn]

As much as I want to post this a lot more than I do, I also am fully cognizant of the fact that the search
feature of the site often does have mixed/odd results...

 

[lewtot184]

The fbo plates I have are VERY inaccurate. Measure to verify the numbers on the plates.

 

[threewood]

440 .040" over, stock stroke. 10.2:1 Using a stock distributor with Pertronix III, welded up my advance plates to get my advance.

21° initial
37° total
All in around 1500 rpms

Runs great on 88 pure gas.

 

[threewood]

I got this one. Feels very plastic but does the job.

View attachment 1645513

View attachment 1645514

I guess I'm old school. I have an old chrome Sears timing light and a tach/dwell meter I use to check advance.

 

[Kern Dog]

Pulling the Hi Rev apart..

The reluctor wheel didn’t want to come off. It is on tight.
The other Hi Rev distributor I have here has a wheel that just slips on and off. This doesn’t bode well for quality control.

I pulled the breaker plate and the T out as one.

The FBO plate in place on 14 degrees.

These distributors come with one medium spring and a softer one, the weights had to shift a bit to get the plate centered.
Back together.

The new curve.

I did gain 15 degrees, not 14. This should be okay. The curve comes in much sooner, that seemed to improve the smoothness of the engine. Time to drive it.

 

[Black_Sheep]

20 initial/36 total all in @ 2500 and no vacuum advance.

 

[toolmanmike]

20 initial/36 total all in @ 2500 and no vacuum advance.

A hot big block up to 38. If it rattles, back it down.

 

[Kern Dog]

20 initial/36 total all in @ 2500 and no vacuum advance.

That is great. Mine is about the same.
Out for a drive, and…..
It idles smoother. It accelerates smoother and faster. Off idle, it feels more responsive. I credit the rapid advance starting right from idle.
This cam is bigger than ideal for the driving that I do. It is 261/271 degrees @ .050 and sure wants to run well past the 6000 rpm point where I start to get nervous.
It isn’t as peppy below 3000 as my last cam, the Mopar Performance 528.
It is more peppy now with the faster advance curve.
I will probably swap cams to something between this and the MP 528.
Not today though.
It appears I’ve hit my limit for starting new topics here.

 

[Black_Sheep]

A hot big block up to 38. If it rattles, back it down.

It makes more power @ 38 with good fuel, but I can't always run good fuel.

 

[toolmanmike]

It makes more power @ 38 with good fuel, but I can't always run good fuel.

Run whatever works for you and your combo.

 

[Jonas Nordstrom]

Thanks for the info and pics Kern. I will tune my curve this summer so this topic/thread really helps.

 

[Some Car Guy]

Regarding chamber design and advance, a close friend had a Sonny Leonard pro stock engine and it made best power at 25 degrees. I don’t know what they are doing today, this was 20-25 years ago.

 

[Kern Dog]

Lat model Hemi engines don't need 35 degrees of timing. Their chambers are efficient and the bores are nowhere near as wide as the old fashioned big blocks!

 

[68 Sport Satellite]

View attachment 1645661

Are you sure that is not the graph showing school class-size numbers and the pay rate of teachers required for that quantity of children???

KD, when you ran it up to 50 degrees that was without Vacuum Advance? And no pinging, but no load either, correct?